The satisfactory removal of soils/stains is a particular challenge to the formulator of a detergent composition for use in a washing process such as laundry or machine dishwashing process.
Traditionally, the removal of soils/stains has been achieved by the use of bleach components such as oxygen bleaches, including hydrogen peroxide and organic peroxyacids, and also by enzyme components.
Oxygen bleaches are known to effectively decolourise pigments from soiled/stained substrates.
Enzymes are also known as effective soil/stain removal agents, for example, in the removal of proteinaceous stains/soils such as blood, egg, chocolate, gravy and the like.
Phosphorus containing compounds such as sodium tripolyphosphate have effective builder properties; however environmental concerns have made the use of phosphorus containing compounds less attractive in detergent compositions.
A problem encountered with the use of high levels of oxygen bleaches is the propensity of these oxygen bleaches to lead to stain fixing and/or darkening. Furthermore, high levels of oxygen bleaches increase the cost of the detergents to the consumer. On the other hand low levels of oxygen bleaches can lead to poor stain/soil removal performance, especially when used in a non-phosphate builder containing composition.
A problem encountered with the use of peroxyacids in machine dishwashing methods is the tarnishing/corrosion of any silverware components of the washload. Such a problem, disclosed in GB Patent Application No 9407533.0, is known in the art. Oxygen bleaches tend to give rise to more of a problem of tarnishing than chlorine bleaches. The level of tarnishing observed can range from slight discoloration of the silverware to the formation of a dense black coating on the surface of the silverware.
A problem encountered with the use of enzymes as components of detergents is that enzyme activity in the wash may be affected by the presence of other detergent components in the wash solution. GB Patent Application No 9407533.0 discloses that enzymes may be degraded by bleach components.
The detergent formulator thus faces the challenge of formulating an environmentally friendly product which maximises soil/stain removal without fixing and/or darkening stains/soils, which avoids degradation of the detergent components and which is also inexpensive.
Pending GB Patent Application No 9407536.3 that forms part of the state of the art under Article 54(3) EPC discloses the use of a bleach containing detergent composition which contains low levels of bleach and bleach activator with higher levels of chelant and enzyme and defines a specific Biological Bleach Index which provides stain removal performance. Specific kinetics of bleach delivery are not disclosed, nor are the means to achieve such kinetics.
Pending GB Patent Application No 9407533.0 that forms part of the state of the art under Article 54(3) EPC discloses the use of an enzyme together with a source of peroxyacid bleach, wherein a means is provided for delaying the release to the wash solution of said peroxyacid bleach relative to the release of said enzyme. The delayed release is provided by coating the source of peroxyacid bleach. The coating may occur on the hydrogen peroxide source itself and/or the peroxyacid bleach precursor itself. Specific ratios of hydrogen peroxide: precursor: protease are not disclosed.
The Applicants have found that the occurrence of soil/stain fixing and/or darkening effects arising from use of peroxyacid bleaches in a washing method is related to the rate of release of the hydrogen peroxide source. A fast rate of release of the hydrogen peroxide source to the wash solution tends to exacerbate soil/stain fixing and/or darkening problems. Whilst reducing the rate of release of the hydrogen peroxide source employed in the wash tends to ameliorate these problems, this is accompanied by a marked negative effect on the bleachable stains/soil removal ability.
The Applicants have now surprisingly found that the provision of an alkalinity source which produces a specific minimum amount of alkaline salts into the wash solution ameliorate these problems when low rate of release of the hydrogen peroxide source to the wash solution is used in combination with organic peroxyacid bleach precursors and proteolytic enzymes.
The Applicants have also found that where a non-phosphate builder-containing detergent composition containing a source of hydrogen peroxide, an organic peroxyacid bleach precursor and a proteolytic enzyme, defined in term of an Hydrogen peroxide Precursor Proteolytic enzyme (HPP) index which relates to the ratios of Hydrogen peroxide, precursor and proteolytic enzyme, together with a high level of an alkalinity source, is employed an enhanced stain/soil removal may be obtained.
The Applicants have also found that the total available oxygen (AvO.sub.2) content in the composition should preferably be less than 1.5% by weight of the composition.
The Applicants have also found that the the further addition of compounds enhances the overall stain/soil removal performance. Such compounds may be selected from amylases, water-soluble organic polymeric polycarboxylic compounds, chelants and mixtures thereof
It is therefore an object of the present invention to provide compositions suitable for use in laundry and machine dishwashing methods having enhanced stain removal.
It is a further object of the invention to provide compositions for use in laundry and machine dishwashing methods wherein said compositions show less propensity to cause stains fixing and/or darkening as well as detergent components degradation.